Reduction of copper ores.



UNITED STATES Patented May 10, 1904;.

PATENT OFFICE.

ERNEST P. CLARK, OF NEW YORK, N. Y., ASSIGNOR OF ONE-HALF TO EDWARDBALTZLEY, OF GLEN ECHO, MARYLAND.

REDUCTION OF COPPER ORES.

SPECIFICATION forming part of Letters Patent No. 759,670, dated May 10,1904.

Application filedSeptamber 10, 1902. Serial No. 122,785. (No specimens.)

To all whom, it may concern:

Be it known that I, ERNEST P. CLARK, a citizen of the United States,residing at the city of New York, in the borough of Manhattan and Stateof New York, have invented certain new and useful Improvements in theReduction of Copper Ores, of which the following is a full, clear, andexact description.

This invention relates to a method of and means for extracting copperfrom low-grade ores of the varieties carrying copper in the form ofcarbonates, oxids, sulfids, and finelydivided metallic copper, andespecially to certain methods and means for securing the copper contentsat the lowest possible cost. In

working with ores of this class it is found that the carbonates, oxids,and metallic copper are readily soluble in the solution generallyemployed, but that the sullids are not soluble without previouslyoxidizing, which is generally accomplished by roasting the ores,

and in all mixed ores of this character when ever it has been attemptedto obtain their values by such processes as herein contemplated thefirst proceeding has almost invariably been to roast the entire body ofore for the purpose of oxidizing that portion of the copper existing assulfids. This entails alarge and unnecessary expense for roasting, whichI eliminate, as hereinafter described. Ores of this character alsousually carry iron, and this has proved an obstacle to nearly allprocesses used for extracting the copper from low-grade ores. I havefound, however, that a certain proportion of sulfate of iron added tothe solution used for leaching prevents to a large extent the solutionfrom attacking the iron contained in the ore and at the same time addsgreatly to the solvent power of the solution on the copper.

My process is in outline as follows: The ore is first pulverized to aproper degree of fineness, then transferred to leaching-tanks of theusual description, and is leached with a solution composed of water,sulfuric acid, and sulfate of iron, prepared as follows: In thestock-tank used for making up solution the proper amount of water isfirst placed, then sulfuric acid is added to the water until the gravityreaches 7 1- to 8 Baum, which requires about six per cent. of ordinarycommercial sulfuric acid. Then sulfate of iron is added in theproportion of about one to one and one-fourth per cent. of the totalweight of water and acid combined. As soon as the sulfate of iron isdissolved the solution is ready for immediate use. It is passed into theleaching-tank on top of the ore and filters through it slowly, comingaway from the filter-bottom as a blue solution, carrying the coppercontents of the ore in the form of sulfate of copper. This solutionpasses at once to the deposition-tanks, where the copper is de positedeither electrolytically or by any other suitable means. The solutionbeing deprived of its copper, or the greater portion thereof, isreturned to the stock-tank and is ready to pass through a second mass ofpulverized ore. The solution in its passage through the ore oxtracts, asbefore stated, all of the copper present as carbonates, oxide, ormetallic copper. The portion of copper present as sullids still remainsin the ore and is insoluble in this solution. The ore is now washed fromthe leaching-tank and passed over concentrators. The sulfids being theheavier part of the ore are readily separated by the concentrators andare then oxidized by roasting or any other suitable means and are thenready to be added to the next charge of ore in one of theleaching-tanks. By this means it is only necessary to roast or otherwiseoxidize the actual sulfids contained in the ore as distinguished fromthe usual proceeding of roasting the entire body of ore, and as in suchores the sullids frequently constitute as little as ten per cent. of thevalues in the ores the saving is very large.

The solution mentioned above of sulfuric acid and water-7t to 8 Baum andone to one and one-fourth per cent. sulfate of iron added-has been foundin practice to have the greatest possible solvent power on the coppercontents of the ore when present in the forms mentioned above, also tohave very little solvent action on the iron contained in the ore. Theresult in practice is that ore can be thoroughly leached by thissolution in four hours, which would require ten or twelve hours ifsimply sulfuric acid and water Were used as a solvent. This solution isvery valuable as facilitating the Work and saving time, causing agreater amount of copper to be extracted with the same size of apparatusin a given time than by the use of other solutions.

Having described my invention, I claim- 1. A process for Working themixed ores of copper, consisting in first leaching the ore law toextract the soluble contents, then concentrating the insoluble portionof the, copper contents, and rendering this portion soluble by oxidizingit and then leaching the same, substantially as described.

